The invention relates to a valve and actuator assembly including particularly simple and advantageous acutating components. The valve and actuator assembly is primarily useful in association with an automatic compression release system for a two-cycle engine, and the invention also contemplates a method of effecting start-up and running of a two-cycle internal combustion engine in a particularly effective manner. As is well known in the art, it is necessary to provide pressure relief in a cylinder of a two-cycle engine during start-up, in order to allow the easiest starting possible. According to the present invention, this compression release is effected in a simple, energy efficient, and reliable manner.
A two-cycle engine, such as a lawn mower engine, includes a cylinder wall with a piston movable (i.e., reciprocal) within the cylinder wall. A crankcase is disposed at a first end of the cylinder wall, and a compression release opening disposed at a second end of the cylinder wall, opposite the first end. The compression release opening is located at approximately 20-30% of the piston stroke from top center.
According to the present invention, a conventional compression release valve assembly is mounted in operative association with the compression release opening. This assembly includes a valve body, a stationary valve seat, a valve actuator stem integral with the valve body, a pressure responsive element (preferably a diaphragm) defining a first chamber and operatively engaging the valve stem, and spring biasing means for biasing the valve body to an open position with respect to the valve seat. According to the present invention, means defining a fluid flow path are provided between the first chamber and a source of vacuum or pressure. Preferably the source of vacuum or pressure is the crankcase.
The means defining the fluid flow path from the diaphragm first chamber to the crankcase includes a one-way valve means (i.e., check valve) which allows flow of fluid from the diaphragm chamber to the crankcase but not vice versa, and an orifice which allows bleeding of fluid in both directions between the diaphragm chamber and the crankcase. The check valve and the orifice are disposed in fluid parallel relationship so that fluid must flow through one or the other between the diaphragm chamber and the crankcase. Preferably the orifice and check valve are disposed in a single fluid element which is mounted within a housing, with hose sections connected to fittings for the housing, the hose sections connecting the housing up to the crankcase and the diaphragm chamber. In this way, the fluid flow path defining structures according to the present invention may be readily retrofit to existing two-cycle engines, as well as being readily replaceable, or removable for inspection and repair.
According to the method of the present invention, easy start-up of a two-cycle engine is provided. The method comprises the steps of: (a) At start-up, providing for the exhaust of fluid from the cylinder through the pressure relief opening, ultimately to be exhausted to the atmosphere. (b) After start-up when the piston is moving at operating speed within the cylinder, providing quick exhaust of fluid from the first chamber of the pressure responsive element, so that the valve moves to a closed position and prevents exhaust of fluid from the cylinder. And, (c) upon stopping of the engine, providing for slow bleed back of fluid to the first chamber so that the valve ultimately returns to an open position. Steps (b) and (c) are preferably accomplished by connecting up the first chamber to the crankcase and providing the check valve and orifice in parallel in a fluid flow path between the crankcase and first chamber.
It is the primary object of the present invention to provide a simple and effective apparatus and method which are particularly adapted for effecting easy start-up--in a reliable manner--of a two-cycle internal combustion engine. This and other objects of the present invention will become clear from an inspection of the detailed description of the drawings, and from the appended claims.